Tampons are well known in the art and are used for feminine hygiene. Also many tampon manufacturing methods and apparatuses have been disclosed in the prior art. Generally, a distinction is made between folded and rolled tampons. The former have improved absorbent characteristics, but possess less strength and are commonly used with an applicator to reduce the chance of tears and other damage to the tampon before insertion. Rolled tampons are slightly less absorbent, but more sturdy and can be applied digitally, as opposed to the folded tampons. Furthermore, measures can be taken to increase the absorbency of the rolled tampons. The invention will focus on uses concerning rolled tampons and intermediate products thereof.
Rolled tampons are manufactured by rolling multiple-layered sheets. The multiple-layered sheets comprise a layer of absorbent material of a certain length, upon which a strip of web material is bonded which has only a fraction of the length of the layer of the absorbent material, thus creating the multiple-layered sheets. An example of this can be seen in FIG. 1A. A further description of this product will be provided later in this document.
It is precisely the difference in length between the absorbent material and the strip of web material that causes problems in the production process and the apparatuses used therefor. Most of these operate under stop-go circumstances, where the shorter strip is provided intermittently to a sealing or bonding station for bonding the strip to the longer absorbent material over parts of these materials. In order to intermittently provide the strips, a conveying system is used which operates under cyclic conditions, whereby a square wave is approximated with relatively short rise and fall time.
First of all, it is desired to attain a maximal production speed, therefore the industry strives for continuous processes, allowing the materials to be conveyed at constant (high) speeds. Intermittent processes would require an acceleration and deceleration each cycle, which would be restricted by mechanical limitations. A continuous process could run at higher speeds compared to a stop-go process, as it would not require such high accelerations and decelerations, as the frequency of these cycles can easily run up to several cycles per second. A high production speed of this part of the system is also necessary, as preceding processes and following processes, and the apparatuses used in them, have improved significantly, while the process of actually creating the multiple-layered sheets has somewhat lagged behind due to the restrictions set by using stop-go processes.
Another consequence of the high frequency of the acceleration and deceleration cycles, and the short rise and fall time of the cycles, is the strain this would impose on the apparatuses operating under such a stop-go process. These apparatuses would be far more prone to mechanical breakdowns, requiring costly repairs and spare parts. Furthermore, a system capable of performing high-frequency stop-go processes will generally be more expensive than a system that runs continuously at constant speeds. Also, apparatuses for stop-go processes will generally require more space than continuous apparatuses.
Thirdly, stop-go processes are much harder to regulate, especially when accurate coordination of the stop-go process with other processes is needed. Small variations easily occur due to the delicate course of the cycle, especially considering the very short period of the cycles, and furthermore due to the high frequency, variations are more likely to show up in some or more products. A continuous process is less sensitive to these variations, resulting in smaller variations if they occur. Furthermore, a continuous process can be more easily monitored and adjusted.
Such a stop-go process is for instance described in DE 3,519,515, where a first material is cut into short strips and affixed to a continuously provided second material. The first material is usually conveyed intermittently by a combination of multiple rollers to eventually be bonded to the second material. This has the aforementioned disadvantages the applicant wishes to avoid. In a second example according to the invention of DE 3,519,515, a fully continuous process is briefly discussed according to FIG. 3. In this single example however, it is not clear how the invention wishes to convey the first material at a first low speed before cutting it into strips, and at the same time, convey the second material at a second, higher, speed than the first speed, as the conveying of the second roller would be executed by the same roller which therefore would rotate at two different speeds if strips are to be provided of a different length than corresponding sections of the second material. As a result, the proposed concept of FIG. 3 would not be able to work and would therefore not enable a continuous process.
A well-known and widely-used prior art process and apparatus for manufacturing tampon blanks or intermediate products thereof has been developed by Ruggli. Herein two separate conveying systems are used, wherein the conveying systems use rollers to guide and pull two web materials, one of which is strongly absorbent. The first web material is divided into strips which are provided intermittently in a stop-go process to the second web material, which has been perforated along transverse lines. It is important to note that the length of the strips is shorter than the length of the segments of the second web material, demarcated by the perforation lines, this being the reason a stop-go process is used at a high frequency and high speeds. As mentioned, the applicant noticed that the use of the Ruggli apparatus and the associated method results in a high strain on the components of the stop-go system, which causes more mechanical breakdowns and significantly higher maintenance costs. Furthermore, the applicant notices that the production speed is capped at a lower rate than is desired, as the systems that follow or precede the Ruggli apparatus can operate at higher speeds and are thus forces to lower their speed to match the Ruggli apparatus.
In a first solution, according to EP 1,308,147, a continuous process is proposed wherein strips are cut and then reoriented (preferably a quarter turn) which comes down to the practical switching of the length and breadth of the strips. This enables the user to run the system for producing strips at an equal speed to a second system that provides a second material to which the strips are bonded in such a way that the length of a strip differs from the length of the second material to which the strip is associated. The disadvantage of this system is that reorienting the strip is a complicated process with a relatively high margin of error, and needs expensive machinery. Furthermore, it requires more space than other systems as the reorienting needs to happen between the cutting of the strips, and the joining of the strips to the second material. In practical applications, these processes are preferably executed as close to each other as possible, both in time as in space.
In a second solution, according to EP 2,260,813, a device is proposed which is capable of gripping the strips and stretching these before applying the strips to a second material. Again, this requires sophisticated, expensive machinery and space, and adds more breakdown points to the process. Furthermore, it offers no real solution as the stretched material will try to revert to its previous state and thus deform the product.
In a third solution, according to EP 1,035,819, a first material is provided continuously to a suction roller at a first speed where the first material is accelerated to a second speed and stretched, and subsequently cut into shorter strips. The strips are conveyed to a second web material, continuously provided at a second speed higher than the first speed, where the strips are bonded to the second web material. Disadvantages of the proposed concept are, as can be seen in the figures, the need for an elaborate system of pre-cutting rollers (for weakening the separation zones of the strips), acceleration rollers (for accelerating and tearing off the separate strips), transfer drums, and a suction drum which is difficult to accurately control. Larger systems are usually more prone to technical failures, due to the multitude of components which affect each other. Furthermore, the longer the path the strips and other items must travel, the more variations can occur which would lead to an incorrect positioning of the strips on the other material. Most importantly however, a stretch-and-separate process for the strips is disadvantageous to the goals of the applicant, namely to provide for a fast, reliable system for producing tampon laminates. If the weakening pre-cuts are not strong enough, the system of EP 1,035,819 does not allow for a very accurate separation of the strips, and in some cases could even cause unwanted tearing, variable edgings and variations in length of the strips. If the weakening pre-cuts are too strong, the strips might tear before reaching the actual acceleration roller which would cause the system to stop and have to be reset again. Even if the pre-cuts are applied to the desired effects, there will still be a variation in each strip due to local characteristics of the strip material, said variations are undesired. Also, the torn edges of the strips will not be as straight and controlled as desired.
There remains a need in the art, and even more so in the industry, for an improved continuous process for manufacturing multiple-layered sheets and tampon blanks, as well as apparatuses capable of performing these processes.
The present invention aims to resolve at least some of the problems mentioned above, by providing methods for a continuous process of intermittently joining strips of a first web material to a continuous second web material and apparatuses capable of performing these processes.